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Tires/LT vs XL Tires

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QUESTION: Hello - I am searching for tires for my 1992 Toyota Pick-up. As I have used Hankook tires on other trucks and found that they hold up to Colorado pretty well. I am looking for a 235 75 R15. I have found the HK Dynapro ATM 235 75 R15XL and a LT 235 75 R15/6. The XL has a higher speed rating and a higher load rating than the LT. The truck currently has LT tires on it and I'm wondering if I can put the XL tires on it rather than the LT tires? I do not quite understand the difference between the XL and LT.  Thanks for any assistance you can provide.

ANSWER: Pat,

First, your truck originally came with a different tire size.  I'm not sure which size as there is quite a list of optional sizes, but you can verify this by looking for the vehicle tire placard, which is usually on a door or doorpost, or in the glove box.  It will list the original tire size and the proper inflation pressure for that size.

I'm going to guess it shows 31x10.50R15LT.  If not, then the rest of this post it going to be incorrect.  Please post a followup in whether or not I am correct, so I can be sure to have given you good advice.

A 235/75R15 can be used in place of a 31X10.50R15LT, but the overall diameter is 7% smaller, so the speedometer will read low.  It will read 64 mph when you are actually doing 60 mph.

But a Standard Load (SL) can be used.  You don't need either an Extra Load (XL), or an LT.

That should increase the number of options.

So let's start there and see where this takes us.


---------- FOLLOW-UP ----------

QUESTION: Thanks Barry.  It came originally with a smaller tire and the 235 is one size up.  I couldn't run the 31x10.5 because the rim is too narrow.  (It's a 4 cylinder 22R as opposed to the V6).  My son has it at school so I can't check the door.

Answer
Pat,

Sorry for the delay in responding.  We had a large lightening strike near the house and it took out several electronic things, including my cable modem.

OK, so the original tires were 225/75R15's.  My sources say that is one of the possibilities.

That means that the vehicle doesn't need XL tires - or LT tires.  It can use SL tires - and that opens a whole realm of possibilities.  

And going up to a 235/75R15 results in a speedometer error of only 2%.  

While this doesn't answer your original question, it does address a bigger question.  

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Barry Smith

Expertise

I have over 30 years experience in the design, manufacturing, and testing of tires. I have served as the technical advisor to the "800" number. I have authored or co-authored many publications - usually without credit. I can answer almost any technical question, but please don`t ask me to compare brands. I probably have prejudices because of my work experience.

Experience

Member SAE (Society of Automotive Engineers) Member Tire Society (Tire Technical Organization) SCCA Regional Competiton License holder Authored many training manuals on tires, their care and use.

Organizations
SAE (Society of Automotive Engineers) SCCA (Sports Car Club of America) Tire Society

Publications
You may want to visit my web site: http://www.barrystiretech.com/index.html

Education/Credentials
I am a graduate of the University of Dayton, Dayton, OH - BME, 1971 I attended graduate school at the University of Akron - but did not complete my PhD - something I regret.

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